(1) Field of the Invention
This invention relates to a canister constituting a vaporized fuel adsorbing system used with an internal combustion engine.
(2) Background of the Invention
A vaporized fuel adsorbing system is one in which vaporized fuel produced in the fuel tank for storing fuel for use in the internal combustion engine is collected on the vaporized fuel adsorbing material, such as activated charcoal, contained in the vaporized fuel adsorbing canister (hereinafter canister, for short), and the vaporized fuel collected on the activated charcoal is drawn by suction into the engine for combustion during engine operation.
The canister comprises a hollow body containing charge of activated charcoal, and a cover attached to the hollow body and formed with a vaporized fuel inlet and a vaporized fuel outlet for introducing the vaporized fuel into the hollow body to be collected on the activated charcoal and for discharging the vaporized fuel from the hollow body respectively. The hollow body is provided at either end thereof with a filter member compactly supporting the activated charcoal and preventing incorporation of dust in the vaporized fuel.
The cover of the canister is fluidly connected to the fuel tank through a rubber tube to allow the vaporized fuel produced in the fuel tank to flow therethrough into the cover. During the process of introduction of the vaporized fuel into the cover, the phenomenon of the vaporized fuel changing into a liquid might occur. The liquefield fuel is high in solubility and tends to dissolve oil, such as a mold releasing agent for the rubber tube and grease for a check valve mounted midway in the rubber tube, so that the liquefied fuel containing the dissolved oil and fat flows along the inner wall surface of the cover into the filter member interposed between the cover and the activated charcoal.
The filter member used is of a fine mesh type (10-80 mesh) formed of unwoven cloth or foamed urethane. Thus the oil and fat, such as the mold releasing agent and grease, incorporated in the liquefied fuel would be gradually accumulated on the filter member, until finally they would obturate the filter member.
Obturation of the filter member raises the serious problem that obstruction of the passage of the vaporized fuel through the filter member prevents the vaporized fuel from being collected on the activated charcoal in the hollow body of the canister.